RetroCode RetroCode - 5 months ago 29
Node.js Question

How can I pass a callback to a generator that I pass to the "vo" library?

I am trying to understand how callbacks work so I created a function and passed a second argument named 'callback', which I call at the end of the function with 'callback(arr)' . However I am getting an error which says : "callback is not a function" ? Can you please tell me what I am doing wrong?


vo is a nodejs library that takes a generator function* () and runs all it's yields . It's basically a way to handle async code with less callbacks (yes I know I used a callback as well but that's pretty much a choice). A more popular library that does exactly the same thing is co. Link to vo:

var Nightmare = require('nightmare');
var vo = require('vo');

function* MyFunction(query, callback) {
arr = [];
for (i = 0; i < 1; i++) {
arr.push(yield Nightmare({
show: true
.inject('js', 'jquery-3.1.0.js')
.evaluate(() => {
var title;
title = 1
extend = 2
var img;
img = 3
var par;
par = 4
url = window.location.href;
var par_arr = [5, 5, 5, 5];

return {
title: title,
img: img,
par: par,
par_arr: par_arr,
url: url

.catch(function(error, nightmare) {

console.error('Search failed:', error);


return arr;

vo(MyFunction)('query', (arr) => {


This is working in my enviroment;

var vo = require('vo');

function* idMaker(query, params){

  for (var i = 0; i < 5; i++) {
 params.callback("callback value");

vo(idMaker)("param value",{callback: (value)=>console.log(value)}  );


param value
param value
param value
param value
param value
callback value

I have no time right now to read 'vo' docs to tell you why but I saw a exaplme here.